Satellite communication terminals typically rely on reflector antennas, which are high gain at relatively low cost. For mobile applications, reflector antennas must be mechanically steered to point the antenna at a desired satellite. However, the mechanical systems for aiming the antenna are bulky and expensive. To improve the performance of mobile satellite terminals and eliminate the need for mechanical steering, mechanically steered antennas can be replaced by a phased array antenna with electronic beam steering.
Mobile satellite terminals often shape the beam of the transmit signal to satisfy regulatory sidelobe pattern mask requirements and avoid interference with the uplink signal impinging on other satellites adjacent to the intended target satellite. This is accomplished by shading or tapering the amplitude of the illumination pattern over the area of the antenna aperture.